/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with this
 * work for additional information regarding copyright ownership. The ASF
 * licenses this file to You under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law
 * or agreed to in writing, software distributed under the License is
 * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied. See the License for the specific language
 * governing permissions and limitations under the License.
 */
package com.sailmi.oss.io;

import java.io.Serializable;

/**
 * Enumeration of IO case sensitivity.
 * <p>
 * Different filing systems have different rules for case-sensitivity. Windows
 * is case-insensitive, Unix is case-sensitive.
 * <p>
 * This class captures that difference, providing an enumeration to control how
 * filename comparisons should be performed. It also provides methods that use
 * the enumeration to perform comparisons.
 * <p>
 * Wherever possible, you should use the <code>check</code> methods in this
 * class to compare filenames.
 *
 * @author Stephen Colebourne
 * @version $Id: IOCase.java 484844 2006-12-08 23:27:18Z ggregory $
 * @since Commons IO 1.3
 */
public final class IOCase implements Serializable {

    /**
     * The constant for case sensitive regardless of operating system.
     */
    public static final IOCase SENSITIVE = new IOCase("Sensitive", true);

    /**
     * The constant for case insensitive regardless of operating system.
     */
    public static final IOCase INSENSITIVE = new IOCase("Insensitive", false);

    /**
     * The constant for case sensitivity determined by the current operating
     * system. Windows is case-insensitive when comparing filenames, Unix is
     * case-sensitive.
     * <p>
     * If you derialize this constant of Windows, and deserialize on Unix, or
     * vice versa, then the value of the case-sensitivity flag will change.
     */
    public static final IOCase SYSTEM = new IOCase("System",
                                                   !FilenameUtils.isSystemWindows());

    /** Serialization version. */
    private static final long serialVersionUID = -6343169151696340687L;

    /** The enumeration name. */
    private final String name;

    /** The sensitivity flag. */
    private final transient boolean sensitive;

    // -----------------------------------------------------------------------
    /**
     * Factory method to create an IOCase from a name.
     *
     * @param name
     *            the name to find
     * @return the IOCase object
     * @throws IllegalArgumentException
     *             if the name is invalid
     */
    public static IOCase forName(String name) {
        if (IOCase.SENSITIVE.name.equals(name)) {
            return IOCase.SENSITIVE;
        }
        if (IOCase.INSENSITIVE.name.equals(name)) {
            return IOCase.INSENSITIVE;
        }
        if (IOCase.SYSTEM.name.equals(name)) {
            return IOCase.SYSTEM;
        }
        throw new IllegalArgumentException("Invalid IOCase name: " + name);
    }

    // -----------------------------------------------------------------------
    /**
     * Private constructor.
     *
     * @param name
     *            the name
     * @param sensitive
     *            the sensitivity
     */
    private IOCase(String name, boolean sensitive) {
        this.name = name;
        this.sensitive = sensitive;
    }

    /**
     * Replaces the enumeration from the stream with a real one. This ensures
     * that the correct flag is set for SYSTEM.
     *
     * @return the resolved object
     */
    private Object readResolve() {
        return forName(name);
    }

    // -----------------------------------------------------------------------
    /**
     * Gets the name of the constant.
     *
     * @return the name of the constant
     */
    public String getName() {
        return name;
    }

    /**
     * Does the object represent case sensitive comparison.
     *
     * @return true if case sensitive
     */
    public boolean isCaseSensitive() {
        return sensitive;
    }

    // -----------------------------------------------------------------------
    /**
     * Compares two strings using the case-sensitivity rule.
     * <p>
     * This method mimics {@link String#equals} but takes case-sensitivity into
     * account.
     *
     * @param str1
     *            the first string to compare, not null
     * @param str2
     *            the second string to compare, not null
     * @return true if equal using the case rules
     * @throws NullPointerException
     *             if either string is null
     */
    public boolean checkEquals(String str1, String str2) {
        if (str1 == null || str2 == null) {
            throw new NullPointerException("The strings must not be null");
        }
        return sensitive ? str1.equals(str2) : str1.equalsIgnoreCase(str2);
    }

    /**
     * Checks if one string starts with another using the case-sensitivity rule.
     * <p>
     * This method mimics {@link String#startsWith(String)} but takes
     * case-sensitivity into account.
     *
     * @param str
     *            the string to check, not null
     * @param start
     *            the start to compare against, not null
     * @return true if equal using the case rules
     * @throws NullPointerException
     *             if either string is null
     */
    public boolean checkStartsWith(String str, String start) {
        return str.regionMatches(!sensitive, 0, start, 0, start.length());
    }

    /**
     * Checks if one string ends with another using the case-sensitivity rule.
     * <p>
     * This method mimics {@link String#endsWith} but takes case-sensitivity
     * into account.
     *
     * @param str
     *            the string to check, not null
     * @param end
     *            the end to compare against, not null
     * @return true if equal using the case rules
     * @throws NullPointerException
     *             if either string is null
     */
    public boolean checkEndsWith(String str, String end) {
        int endLen = end.length();
        return str.regionMatches(!sensitive,
                                 str.length() - endLen,
                                 end,
                                 0,
                                 endLen);
    }

    /**
     * Checks if one string contains another at a specific index using the
     * case-sensitivity rule.
     * <p>
     * This method mimics parts of
     * {@link String#regionMatches(boolean, int, String, int, int)} but takes
     * case-sensitivity into account.
     *
     * @param str
     *            the string to check, not null
     * @param strStartIndex
     *            the index to start at in str
     * @param search
     *            the start to search for, not null
     * @return true if equal using the case rules
     * @throws NullPointerException
     *             if either string is null
     */
    public boolean checkRegionMatches(String str,
                                      int strStartIndex,
                                      String search) {
        return str.regionMatches(!sensitive,
                                 strStartIndex,
                                 search,
                                 0,
                                 search.length());
    }

    /**
     * Converts the case of the input String to a standard format. Subsequent
     * operations can then use standard String methods.
     *
     * @param str
     *            the string to convert, null returns null
     * @return the lower-case version if case-insensitive
     */
    String convertCase(String str) {
        if (str == null) {
            return null;
        }
        return sensitive ? str : str.toLowerCase();
    }

    // -----------------------------------------------------------------------
    /**
     * Gets a string describing the sensitivity.
     *
     * @return a string describing the sensitivity
     */
    public String toString() {
        return name;
    }

}
